Antenna system for radiating doppler coded pattern using multiple beam antenna

ABSTRACT

Disclosed is an antenna system for radiating a frequency coded or &#39;&#39;&#39;&#39;Doppler&#39;&#39;&#39;&#39; pattern of wave energy into a region of space using a multiple-beam antenna unit. The system radiates a pattern in which the radiated frequency varies as a function of angular direction from the antenna unit. The system uses an antenna unit capable of radiating simultaneous multiple beams and having a separate input port associated with each beam. The frequency coded pattern is achieved during a time period by simultaneously supplying wave energy signals having a varying phase in relation to each other to the antenna input ports.

United States Patent Hannan et al.

[451 Feb. 4, 1975 [75] Inventors: Peter W. Hannan; Harold A.

Wheeler, both of Smithtown, NY.

[73] Assignee: Hazeltine Corporation, Greenland,

[22] Filed: Apr. 3, 1973 [21] Appl. N0.: 347,506

[56] References Cited UNITED STATES PATENTS 3,460,145 8/1969 Johnson343/100 SA CONTROL UNIT l7 3,465,337 9/1969 Tanaka et al. 343/100 SAPrimary Examiner-Maynard R. Wilbur Assistant ExaminerRichard E. Berger[57] ABSTRACT Disclosed is an antenna system for radiating a frequencycoded or Doppler pattern of wave energy into a region of space using amultiple-beam antenna unit. The system radiates a pattern in which theradiated frequency varies as a function of angular direction from theantenna unit. The system uses an antenna unit capable of radiatingsimultaneous multiple beams and having a separate input port associatedwith each beam. The frequency coded pattern is achieved during a timeperiod by simultaneously supplying wave energy signals having a varyingphase in relation to each other to the antenna input ports.

16 Claims, 4 Drawing Figures PATENTEDFEB 4W5 3,864,679

SHEET 1 OF 2 CONTROL UNIT l7 FIG. I

PHASE PERIOD I 0/ SIGNAL A 0 Q SIGNAL B 0 SIGNAL 0 (REFERENCE) TIME FIG.2

ANTENNA SYSTEM FOR RADIATING DOPPLER CODED PATTERN USING MULTIPLE BEAMANTENNA CROSS REFERENCE TO RELATED APPLICATIONS The present inventionrelates to antenna systems ra diating Doppler coded patterns usingmultiple beam antennas, one form of which is described in co-pending US.application Ser. No. 347,505. filed Apr. 3. I973. entitled AntennaSystem For Radiating Multiple Planar Beams," which is assigned to thesame assignee as the present application.

BACKGROUND OF THE INVENTION This invention relates to systems fordetermining the angular position of a target with respect to a referencelocation. In particular this invention relates to systems which use afrequency coded pattern to perform angle measurement, also known asDoppler systems. In a Doppler system an antenna radiates wave energyinto a region of space in a pattern wherein the frequency of radiationvaries with one of the angular components of direction from the antenna.Frequency coded radiation has in the past been achieved by radiatingwave energy sequentially from the individual antenna elements of anarray. This causes apparent motion of the radiation source, resulting ina Doppler frequency shift which depends on the relative angle of thetarget with respect to the antenna.

Some deficiencies associated with'the sequentially excited array antennafor generating Doppler signals v are difficulty in controlling beamshape and complexity in construction. A multiple beam antenna radiatinga different frequency on each beam would appear to be an attractivemethod for radiating a Doppler coded pattern. This method could use asimpler antenna unit and have better control over pattern shape andcoding. An attempt to continuously radiate different frequencies on thevarious beams ofa multiple beam antenna would result in randominterference between the radiated signals, resulting in widely varyingsignal amplitude and failure of coding.

SUMMARY OF THE INVENTION It is an object of this invention, therefore,to provide a new and improved antenna system for radiating a Dopplerpattern into a region of space from a multiple beam antenna.

It is a further object of this invention to provide such a systemwherein the radiated signal has a substantially constant amplitudeversus time characteristic during a time period.

It is a still further object of this invention to provide such a systemwherein the radiated pattern can be shaped to coincide with the desiredregion of space.

In accordance with the invention, there is provided an antenna systemfor radiating wave energy into a desired region of space in a desiredradiation pattern during a selected time period. The desired pattern isone in which the frequency of the radiated energy within the region ofspace varies with at least one of the components of angular directionfrom the antenna system. The antenna system includes an antenna unitcapable of radiating a plurality of beams in different directions withinthe region of space from a common aperture.

and having a plurality of wave energy input ports, such that each of theports corresponds to one of the beams. The antenna system additionallyincludes means for simultaneously supplying a plurality of wave energysignals during the time period, one to each of the ports of the antennaunit, with each of the signals having a phase. measured with respect tothe phase of the wave energy signal supplied to the port correspondingto an adjacent antenna beam. which varies during said time periodbetween a predetermined pair of values. the variation being less than360 and the sense of the variation being alike for pairs of antennaports corresponding to similarly adjacent beams. When these signals aresupplied to the antenna ports. the antenna radiates the desiredradiation pattern.

For a better understanding of the present invention. together with otherand further objects thereof, reference is had to the followingdescription taken in conjunction with the accompanying drawings. and itsscope will be pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is one embodiment of an antennasystem constructed in accordance with the present invention.

FIG. 2 is a diagram illustrating the phase of wave energy signals usedin conjunction with the FIG. I antenna.

FIG. 3 illustrates the operation of the FIG. 1 antenna.

FIG. 4 is an alternative embodiment of the present invention.

DESCRIPTION AND OPERATION OF THE FIG. I ANTENNA SYSTEM The antennasystem of FIG. 1 includes an antenna unit consisting of a plurality offeedhorns 10a, b, c for illuminating a focusing reflector 11. Thefeedhorns 10 are located near the focal axis of the paraboliccylindrical reflector I1 and displaced from each other such that waveenergy from each feedhorn I0 illuminates the reflector 11 and causes abeam to be radiated at a different angle in space with respect to theantenna syste'rn. This type of antenna unit is more fully described andcovered by the above referenced co-pending application.

Associated with each of the feedhorns I0 are corresponding wave energyinput ports 12a, b, 0. Each of these input ports 12 are connected to acorresponding one of the phase shifters 14a, b, c by suitabletransmission lines 13a, b, c. An oscillator 15 supplies wave energysignals to a power divider 16. The wave energy signals from the outputsof the power divider 16 are supplied to the phase shifters 14. Varyingphase control signals are generated by control unit 17 and supplied tocontrol inputs of the phase shifters 14. Thus, the wave energy signalssupplied to the phase shifters 14 have their phase shifted in relationto each other in accordance with the phase control signals such thatsignals with varying phase in relation to each other are supplied bytransmission lines 13 to the input ports 12 of the feedhorns 10.

The oscillator 15, power divider 16, phase shifters I4, transmissionlines 13 and control unit 17 together comprise means for simultaneouslysupplying a plurality of wave energy signals. one to each of the ports12 of the antenna unit. with each of the wave energy signals having apredetermined varying phase in relation to any other of said signals.

Each of the feedhorns in FIG. 1 is designed to illuminate the reflector11, which forms a common aperture. The antenna unit radiates a beam foreach of the feedhorns 10 in a direction which is unique to each of thefeedhorns by reason of the displacement of the feedhorns 10 from eachother as explained more fully in the aforementioned copendingapplication. Each of the input ports 12 of the feedhorns 10 is thereforeassociated with an antenna beam.

Those skilled in the art will recognize that other types of multiplebeam antennas may be substituted for the antenna unit shown in FIG. 1.The antenna must be capable of radiating a plurality of beams indifferent directions within a desired region of space from a commonaperture, and have a plurality of wave energy input ports such that eachof the ports corresponds to one of the beams. Antennas of this type maybe conveniently referred to as Beamport antennas.

The transmission lines 13 may be any type appropriate for use at theoperating frequency chosen for the antenna system. It is important,however. in the FIG. 1 embodiment that these transmission lines have aphase length in relation to each other which is appropriate forsupplying the wave energy signals to the ports 12 with the requiredvarying phase in relation to each other.

The phase shifters 14 may be any type which is appropriate for thefrequency of the wave energy signals. Example of suitable phase shiftersare ferrite phase shifters and diode phase shifters, both of which usephase control signals to vary their apparent electrical length andthereby phase shift the wave energy signals. The phase control signalssupplied by the control unit 17 should be signals appropriate forcontrolling the phase shifters 14 selected for use in the antennasystem. These signals may be digital logic signals or analog signalsaccording to the type of phase shifters selected.

The oscillator may be any suitable generator of wave energy signals atthe chosen operating frequency. The power divider may be any of thecommonly used types. well known in the art. such as couplers, T"junctions or reactive dividers.

It will be evident that other means may be used to supply the necessarywave energy signals with a varying phase in relation to each other. Forexample, phase control may be performed at a different frequency thanthe radiated frequency and using frequency converting devices, or byperforming a digital or analog frequency synthesis to generate therequired signals. Phase control may also be achieved by using mixingdevices rather than phase shifters.

FIG. 2 illustrates typical varying phase of the signals supplied to theinput ports 12 of the FIG. 1 antenna. Phase is shown in relation to thephase of signal C, which would be supplied to the input port 12c, forexample. As is evident from the diagram, the phase of the signals A" andB," which would be supplied to input ports 12a and 1212, respectively,have a varying phase in relation to the phase of the signal C and inrelation to each other. As shown in FIG. 2, the sense of phase variationfor the signals supplied to each port with respect to an adjacent portis alike for pairs of antenna ports corresponding to similarly adjacentbeams. Consequently. signal A, supplied to port 1011 has a positivephase variation with respect to signal b supplied to port 10b. Likewise,signal 8" has a positive phase variation with respect to signal C"supplied to port 10c. The phase of the signals during a period nominallyvaries linearly from a first predetermined phase point for each of thesignals to a second predetermined point for each of the signals. Thephase variation may depart from a linear variation to account forparticular characteristics of various antennas such as defocusing ornonequal spacing of the feedhorns. etc. The phase variation period maybe continuously repeated as shown in FIG. 2 to produce a substantiallycontinuous frequency coding.

It should be noted that during any particular period the effect of thelinear phase variation is to cause a frequency change in thecorresponding wave energy signal. However, it is not effective tocontinuously supply wave energy signals of different frequency to theinput ports of the antenna to cause the desired radiation pattern,because the phase relation necessary to prevent interference of thesignals in the various beams is only present during a particular period.To prevent interference between adjacent beams it is necessary that thephase between the signals supplied to ports corresponding to adjacentbeams never be such that the adjacent beams are l out of phase.Consequently. the total phase variation between adjacent ports can neverexceed 360 and is usually much less than 360.

Doppler frequency coding is most often associated with an antenna whichradiates energy from a moving radiation source. FIG. 3 illustrates asectional view of the antenna unit used in the FIG. 1 antenna system. Atthe beginning of a period the phase of the wave energy signals suppliedto the feedhorns l0 combine when radiated from the feedhorns to form aradiation phase front 18a which proceeds in the direction 190, toilluminate an area around the point 20a on the reflector 11. During theperiod the phase of the wave energy supplied to the feedhorns l0 varies,as shown in FIG. 2, causing the illuminated area to move verticallyacross the reflector. At the end of the period the phase of the waveenergy signals supplied to the feedhorns 10 form the phase front 18);,which proceeds in a direction 1%, to illuminate an area around point 20bon the reflector. This process may be repeated for several periods,causing the illuminated area on the reflector 11 to repeatedly move fromthe vicinity around the point 20a to the vicinity around the point 20b.Points 20a and 20b are shown by way of example in FIG. 3. Theilluminated area may center around any points on the section of thereflector. This motion of the illuminated area on the reflector causesthe antenna system to radiate a pattern similar to a sequentiallyexcited array wherein the frequency of radiation varies with one of theangular components of direction from the antenna.

The group of feedhorns 10 may be considered to be a phased array forilluminating the reflector 11 and array design principles are thereforeapplicable. The spacing between the feedhorns should be chosen such thatthere will be no grating lobes on the reflector when the feedhorns areexcited by any of the phase relations associated with a period. Thenumber of feedhorns required is a function of the angular region ofspace within which it is desired to radiate the frequency coded pattern.A larger number of feedhorns would cause a narrower illuminated area andhence a larger angular region in which the frequency coded pattern wouldbe radiated. Other tradeoffs will be evident to those skilled in theart. For example, the time duration of the phase variation period isdependent on the amount of frequency shift desired in the radiatedpattern. The shape and size of the reflector 11 and feedhorns aredependent on the region of coverage and beamshape desired. The use ofother feed elements in place of feedhorns and other means for focusingwave energy in place of a parabolic reflector will be evident to thoseskilled in the art.

DESCRIPTION AND OPERATIONS OF THE FIG. 4

ANTENNA SYSTEM FIG. 4 illustrates another embodiment of an antennasystem constructed in accordance with the present invention. In the FIG.4 system. wave energy signals are supplied to the antenna ports 21a, b.c. d by similar devices l4-l7 as in the FIG. 1 antenna. The principaldifference is that the antenna unit in the FIG. 4 embodiment comprisesan array of antenna elements 22 which are coupled to the antenna ports21 by a Bulter Matrix 23. The properties of a Butler Matrix are wellknown in the art. Basically, each of the input ports 21 is coupled tothe antenna elements 22 by the Bulter Matrix 23 such that wave energysignals supplied to each of the ports 21 will be radiated by theelements 22 in a beam which is in a direction unique to that port. Thus,the antenna unit in the FIG. 4 embodiment has the same generalcharacteristics as the antenna unit in the FIG. 1 embodiment, that is,they are both "Beamport" antennas, although different in form.

Wave energy signals having varying phase in relation to each other, whensimultaneously supplied to the antenna ports 21 in FIG. 4, will causewave energy signals to be sequentially supplied to the elements 22 ofthe aperture in a manner resulting in an apparent motion of theradiation source. This operation is evident because of the nature of thetransformation performed by the Bulter Matrix 23.

Other variations in antenna systems which embody the present inventionwill be evident to those skilled in the art. Other matrices can be usedto provide the necessary multiple-beam, multiple-port antenna function,including those which operate at a different frequency than the desiredfrequency of radiation in conjunction with devices for frequencyconversion. Also, devices which are not matrices of themselves, such asenclosed lenses, but have the same properties byreason of transmissioncharacteristics can be used in an antenna system constructed inaccordance with the present invention. i

In describing the various embodiments above, reference has been made totransmitting antenna systems, but it will be recognized by those skilledin the art that the principles of the present invention can also beapplied to receiving antenna systems. Accordingly, the appended claimsshall be construed as covering both transmitting and receiving antennasystems regardless of the descriptive terms actually used therein.

While there have been described what are at present considered to be thepreferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention and it is, therefore, aimedto cover all such changes and modifications as fall within the truespirit and scope of the invention.

What is claimed is:

1. An antenna system for radiating wave energy into a desired region ofspace during a selected time period in a desired radiation pattern,wherein the frequency of LII said radiated energy within said region ofspace varies with at least one of the components of angular directionfrom said antenna system comprising:

an antenna unit capable of radiating a plurality of beams in differentdirections within said region of space from a common aperture, andhaving a plurality of wave energy input ports such that each of saidports corresponds to one of said beams;

and means for simultaneously supplying a plurality of wave energysignals during said time period, one to each of said ports of saidantenna unit, each ofsaid wave energy signals having a phase, measuredwith respect to the phase of the wave energy signal supplied to the portcorresponding to an adjacent antenna beam, which varies during said timeperiod between a predetermined pair of values, said variation being lessthan 360 and the sense of said variation being alike for pairs ofantenna ports corresponding to similarly adjacent beams;

whereby when said signals are supplied to said antenna ports, saidantenna radiates said desired radiation pattern. 2. An antenna systemfor radiating wave energy into a desired region of space during aselected time period in a desired radiation pattern, wherein thefrequency of said radiated energy within said region of space varieswith at least one of the components of angular direction from saidantenna system comprising:

an antenna unit capable of radiating a plurality of beams in differentdirections within said region of space from a common aperture, andhaving a plurality of wave energy input ports such that each of saidports corresponds to one of said beams;

means for individually controlling the phase of wave energy signalssupplied to each of the ports of said antenna unit such that each ofsaid wave energy signals has a phase, measured with respect to the phaseof the wave energy signal supplied to the port corresponding to anadjacent antenna beam, which varies during said time period between apredetermined pair of values, said variation being less than 360 and thesense of said variation being alike for pairs of antenna portscorresponding to similarly adjacent beams;

and means for simultaneously supplying wave energy signals during saidtime period to said antenna ports via said phase control means;

whereby when said wave energy signals are controlled by said phasecontrol means and supplied to said antenna ports, said antenna radiatessaid desired radiation pattern.

3. An antenna system as specified in claim 2 wherein each of said waveenergy signals is controlled to have a phase which varies linearly withtime between said predetermined pair of values.

4. An antenna system as specified in claim 2 wherein said wave energysignals are supplied to the ports of said antenna during a succession ofsaid periods.

5. An antenna system as specified in claim 2 wherein said means forcontrolling the phase of the supplied wave energy signals comprises aplurality of phase shifters and means for controlling said phaseshifters.

6. An antenna system for radiating wave energy into a desired region ofspace during a selected time period in a desired radiation patternwherein the frequency of said radiated energy within said region ofspace varies with at least one of the components of angular directionfrom said antenna system, comprising:

an antenna unit capable of radiating a plurality of beams in differentdirections within said region of space from a common aperture andcomprising means for focusing incident wave energy and a plurality offeed elements, each having a wave energy input port, for illuminatingsaid focusing means with wave energy patterns such that each of saidfeed elements corresponds to one of said beams;

means for individually controlling the phase of wave energy signalssupplied to each of the ports of said antenna unit such that each ofsaid wave energy signals has a phase. measured with respect to the phaseof the wave energy signal supplied to the port corresponding to anadjacent antenna beam. which varies during said time period between apredetermined pair of values, said variation being less than 360 and thesense of said variation being alike for pairs of antenna portscorresponding to similarly adjacent beams;

and means for simultaneously supplying wave energy signals during saidtime period to said ports via said phase control means;

whereby when said wave energy signals are controlled by said phasecontrol means and supplied to said ports, said antenna unit radiatessaid desired radiation pattern.

7. An antenna system for radiating wave energy into a desired region ofspace during a selected time period in a radiation pattern wherein thefrequency of said radiated energy within said region of space varieswith at least one of the components of angular direction from saidantenna system comprising:

an antenna unit capable of radiating a plurality of beams in differentdirections within said region of space from a common aperture andcomprising a parabolic cylindrical reflector for focusing incident waveenergy and a plurality of feed elements, each having a wave energy inputport, for illuminating said reflector with wave energy patterns suchthat each of said feed elements corresponds to one of said beams;

a number of phase shifters equal to the number of said feed elements forindividuallly controlling the phase of wave energy signals supplied toeach of the ports of said antenna unit;

means for controlling said phase shifters such that the phase of waveenergy signals supplied to each of said phase shifters is shifted to aphase, measured with respect to the phase of the wave energy signalsupplied to the port corresponding to an adjacent antenna beam, whichvaries during said time period between a predetermined pair of values,said variation being less than 360 and the sense of said variation beingalike for pairs of antenna ports corresponding to similarly adjacentbeams;

and means for simultaneously supplying wave energy signals during saidtime period to said ports via said phase shifters;

whereby when said wave energy signals are controlled by said phaseshifters and supplied to said ports, said antenna unit radiates saiddesired radiation pattern.

8. An antenna system for radiating wave energy into a desired region ofspace during a selected time period in a desired radiation patternwherein the frequency of 8 said radiated energy within said region ofspace varies with at least one of the components of angular directionfrom said antenna system. comprising:

an antenna unit capable of radiating a plurality of beams in differentdirections within said region of space from a common aperture andcomprising an array of antenna elements, a plurality of wave energyinput ports and means for coupling each of said ports to said elementssuch that each of said ports corresponds to one of said beams;

means for individually controlling the phase of wave energy signalssupplied to each of said antenna ports such that each of said waveenergy signals has a phase measured with respect to the phase of thewave energy signal supplied to the port corresponding to an adjacentantenna beam, which varies during said time period between apredetermined pair of values, said variation being less than 360 and thesense of said variation being alike for pairs of antenna portscorresponding to similarly adjacent beams;

means for simultaneously supplying wave energy signals during said timeperiod to said antenna ports via said phase control means;

whereby when said wave energy signals are controlled by said phasecontrol means and supplied to said antenna ports, said antenna unitradiates said desired radiation pattern.

9. An antenna system, as specified in claim 8 wherein the means forcoupling said antenna ports to said elements comprises a matrixoftransmission lines and couplers.

10. An antenna system for radiating wave energy into a desired region ofspace during a selected time period in a desired radiation pattern,wherein the frequency of said radiated wave energy within said region ofspace varies with at least one of the components of angular directionfrom said antenna system, comprising:

an antenna unit capable of radiating a plurality of beams in differentdirections within said region of space from a common aperture andcomprising a linear array of antenna elements, spaced from each other bysubstantially equal distances, a number of wave energy input ports,equal to the number of antenna elements, and a Bulter Matrix forcoupling each of said ports to all of said elements, such that each ofsaid ports corresponds to one of said beams;

a number of phase shifters, equal to the number of said ports forindividually controlling the phase of wave energy signals supplied toeach of the ports of said antenna unit;

means for controlling said phase shifters such that the phase of waveenergy signals supplied to each of said phase shifters is shifted to aphase, measured with respect to the phase of the wave energy signalsupplied to the port corresponding to an adjacent antenna beam. whichvaries during said time period between a predetermined pair of values,said variation being less than 360 and the sense of said variation beingalike for pairs of antenna ports corresponding to similarly adjacentbeams;

and means for simultaneously supplying wave energy signals during saidtime period to said ports via said phase shifters;

whereby when said wave energy signals are controlled by said phaseshifters and supplied to said ports, said antenna unit radiates saiddesired radiation pattern.

11. An antenna system as specified in claim 6 wherein said predeterminedpair of values for the phase of the wave energy supplied to each of saidports comprises a first phase value selected to cause the wave energyradiated by all of said feed elements to form a phase front forilluminating a first selected area on said focusing means and a secondphase value selected to cause the wave energy radiated by all of saidfeed elements to form a phase front for illuminating a second selectedarea on said focusing means.

12. An antenna system as specified in claim ll wherein each of said waveenergy signals is controlled to have a phase which varies linearly withtime between said predetermined pair of values.

13. An antenna system as specified in claim 7 wherein said predeterminedpair of values for the phase of wave energy supplied to each of saidports comprises a first phase value selected to cause the wave energyradiated by all of said feed elements to form a phase front forilluminating a first selected area on said reflector and a second phasevalue selected to cause the wave energy radiated by all of said feedelements to form a phase front for illuminating a second selected areaon said reflector.

14. An antenna system as specified in claim 13 wherein said first andsecond selected areas on said reflector are displaced from each other ina direction which is perpendicular to the focal axis of said reflector.

15. An antenna system as specified in claim 14 wherein each of said waveenergy signals is controlled to have a phase which varies linearly withtime between said predetermined pair of values.

16. An antenna system as specified in claim 7 wherein said wave energysignals are supplied to the ports of said antenna during a succession ofsaid periods.

1. An antenna system for radiating wave energy into a desired region ofspace during a selected time period in a desired radiation pattern,wherein the frequency of said radiated energy within said region ofspace varies with at least one of the components of angular directionfrom said antenna system comprising: an antenna unit capable ofradiating a plurality of beams in different directions within saidregion of space from a common aperture, and having a plurality of waveenergy input ports such that each of said ports corresponds to one ofsaid beams; and means for simultaneously supplying a plurality of waveenergy signals during said time period, one to each of said ports ofsaid antenna unit, each of said wave energy signals having a phase,measured with respect to the phase of the wave energy signal supplied tothe port corresponding to an adjacent antenna beam, which varies duringsaid time period between a predetermined pair of values, said variationbeing less than 360* and the sense of said variation being alike forpairs of antenna ports corresponding to similarly adjacent beams;whereby when said signals are supplied to said antenna ports, saidantenna radiates said desired radiation pattern.
 2. An antenna systemfor radiating wave energy into a desired region of space during aselected time period in a desired radiation pattern, wherein thefrequency of said radiated energy within said region of space varieswith at least one of the components of angular direction from saidantenna system comprising: an antenna unit capable of radiating aplurality of beams in different directions within said region of spacefrom a common aperture, and having a plurality of wave energy inputports such that each of said ports corresponds to one of said beams;means for individually controlling the phase of wave energy signalssupplied to each of the ports of said antenna unit such that each ofsaId wave energy signals has a phase, measured with respect to the phaseof the wave energy signal supplied to the port corresponding to anadjacent antenna beam, which varies during said time period between apredetermined pair of values, said variation being less than 360* andthe sense of said variation being alike for pairs of antenna portscorresponding to similarly adjacent beams; and means for simultaneouslysupplying wave energy signals during said time period to said antennaports via said phase control means; whereby when said wave energysignals are controlled by said phase control means and supplied to saidantenna ports, said antenna radiates said desired radiation pattern. 3.An antenna system as specified in claim 2 wherein each of said waveenergy signals is controlled to have a phase which varies linearly withtime between said predetermined pair of values.
 4. An antenna system asspecified in claim 2 wherein said wave energy signals are supplied tothe ports of said antenna during a succession of said periods.
 5. Anantenna system as specified in claim 2 wherein said means forcontrolling the phase of the supplied wave energy signals comprises aplurality of phase shifters and means for controlling said phaseshifters.
 6. An antenna system for radiating wave energy into a desiredregion of space during a selected time period in a desired radiationpattern wherein the frequency of said radiated energy within said regionof space varies with at least one of the components of angular directionfrom said antenna system, comprising: an antenna unit capable ofradiating a plurality of beams in different directions within saidregion of space from a common aperture and comprising means for focusingincident wave energy and a plurality of feed elements, each having awave energy input port, for illuminating said focusing means with waveenergy patterns such that each of said feed elements corresponds to oneof said beams; means for individually controlling the phase of waveenergy signals supplied to each of the ports of said antenna unit suchthat each of said wave energy signals has a phase, measured with respectto the phase of the wave energy signal supplied to the portcorresponding to an adjacent antenna beam, which varies during said timeperiod between a predetermined pair of values, said variation being lessthan 360* and the sense of said variation being alike for pairs ofantenna ports corresponding to similarly adjacent beams; and means forsimultaneously supplying wave energy signals during said time period tosaid ports via said phase control means; whereby when said wave energysignals are controlled by said phase control means and supplied to saidports, said antenna unit radiates said desired radiation pattern.
 7. Anantenna system for radiating wave energy into a desired region of spaceduring a selected time period in a radiation pattern wherein thefrequency of said radiated energy within said region of space varieswith at least one of the components of angular direction from saidantenna system comprising: an antenna unit capable of radiating aplurality of beams in different directions within said region of spacefrom a common aperture and comprising a parabolic cylindrical reflectorfor focusing incident wave energy and a plurality of feed elements, eachhaving a wave energy input port, for illuminating said reflector withwave energy patterns such that each of said feed elements corresponds toone of said beams; a number of phase shifters equal to the number ofsaid feed elements for individuallly controlling the phase of waveenergy signals supplied to each of the ports of said antenna unit; meansfor controlling said phase shifters such that the phase of wave energysignals supplied to each of said phase shifters is shifted to a phase,measured with respect to the phase of the wave energy signal supplied tothe port corresponding to an adjacent antenna beam, wHich varies duringsaid time period between a predetermined pair of values, said variationbeing less than 360* and the sense of said variation being alike forpairs of antenna ports corresponding to similarly adjacent beams; andmeans for simultaneously supplying wave energy signals during said timeperiod to said ports via said phase shifters; whereby when said waveenergy signals are controlled by said phase shifters and supplied tosaid ports, said antenna unit radiates said desired radiation pattern.8. An antenna system for radiating wave energy into a desired region ofspace during a selected time period in a desired radiation patternwherein the frequency of said radiated energy within said region ofspace varies with at least one of the components of angular directionfrom said antenna system, comprising: an antenna unit capable ofradiating a plurality of beams in different directions within saidregion of space from a common aperture and comprising an array ofantenna elements, a plurality of wave energy input ports and means forcoupling each of said ports to said elements such that each of saidports corresponds to one of said beams; means for individuallycontrolling the phase of wave energy signals supplied to each of saidantenna ports such that each of said wave energy signals has a phase,measured with respect to the phase of the wave energy signal supplied tothe port corresponding to an adjacent antenna beam, which varies duringsaid time period between a predetermined pair of values, said variationbeing less than 360* and the sense of said variation being alike forpairs of antenna ports corresponding to similarly adjacent beams; meansfor simultaneously supplying wave energy signals during said time periodto said antenna ports via said phase control means; whereby when saidwave energy signals are controlled by said phase control means andsupplied to said antenna ports, said antenna unit radiates said desiredradiation pattern.
 9. An antenna system, as specified in claim 8 whereinthe means for coupling said antenna ports to said elements comprises amatrix of transmission lines and couplers.
 10. An antenna system forradiating wave energy into a desired region of space during a selectedtime period in a desired radiation pattern, wherein the frequency ofsaid radiated wave energy within said region of space varies with atleast one of the components of angular direction from said antennasystem, comprising: an antenna unit capable of radiating a plurality ofbeams in different directions within said region of space from a commonaperture and comprising a linear array of antenna elements, spaced fromeach other by substantially equal distances, a number of wave energyinput ports, equal to the number of antenna elements, and a BulterMatrix for coupling each of said ports to all of said elements, suchthat each of said ports corresponds to one of said beams; a number ofphase shifters, equal to the number of said ports for individuallycontrolling the phase of wave energy signals supplied to each of theports of said antenna unit; means for controlling said phase shifterssuch that the phase of wave energy signals supplied to each of saidphase shifters is shifted to a phase, measured with respect to the phaseof the wave energy signal supplied to the port corresponding to anadjacent antenna beam, which varies during said time period between apredetermined pair of values, said variation being less than 360* andthe sense of said variation being alike for pairs of antenna portscorresponding to similarly adjacent beams; and means for simultaneouslysupplying wave energy signals during said time period to said ports viasaid phase shifters; whereby when said wave energy signals arecontrolled by said phase shifters and supplied to said ports, saidantenna unit radiates said desired radiation pattern.
 11. An antennasystem as specified in claim 6 whErein said predetermined pair of valuesfor the phase of the wave energy supplied to each of said portscomprises a first phase value selected to cause the wave energy radiatedby all of said feed elements to form a phase front for illuminating afirst selected area on said focusing means and a second phase valueselected to cause the wave energy radiated by all of said feed elementsto form a phase front for illuminating a second selected area on saidfocusing means.
 12. An antenna system as specified in claim 11 whereineach of said wave energy signals is controlled to have a phase whichvaries linearly with time between said predetermined pair of values. 13.An antenna system as specified in claim 7 wherein said predeterminedpair of values for the phase of wave energy supplied to each of saidports comprises a first phase value selected to cause the wave energyradiated by all of said feed elements to form a phase front forilluminating a first selected area on said reflector and a second phasevalue selected to cause the wave energy radiated by all of said feedelements to form a phase front for illuminating a second selected areaon said reflector.
 14. An antenna system as specified in claim 13wherein said first and second selected areas on said reflector aredisplaced from each other in a direction which is perpendicular to thefocal axis of said reflector.
 15. An antenna system as specified inclaim 14 wherein each of said wave energy signals is controlled to havea phase which varies linearly with time between said predetermined pairof values.
 16. An antenna system as specified in claim 7 wherein saidwave energy signals are supplied to the ports of said antenna during asuccession of said periods.